Expression of pres2/S antigen of hepatitis B virus isolated from Pakistan in yeast cells

Recombinant vaccines are an indispensable component of disease management of Hepatitis B infection. Genetic evolution of Hepatitis B Virus (HBV) necessitates the production of new types of antigens for next generation vaccine. This study aimed the expression of HBV middle surface (PreS2/S) protein in Pichia pastoris for production of an antigen for improved HBV vaccine formulation. A PreS2/S antigen-gene was cloned into a vector (pPICZA-alpha) for secretory expression in P. pastoris. Expression of recombinant P. pastoris was optimized under control of AOX1 promoter to produce PreS2/S recombinant protein, which was purified through column chromatography. Specificity of the protein was confirmed through SDS-PAGE, western blot and ELISA. For immunization study, recombinant PreS2/S antigen and commercially available HBV vaccine comprising HBsAg alone were injected to immunize four groups of rabbits. The results of analysis of immunization showed that recombinant PreS2/S protein produced double antibody-titer than that of commercially available HBsAg indicating that PreS2/S antigen could be an ideal candidate for new generation HBV vaccines. This is the first report of secretary expression of biologically active PreS2/S antigen in P. pastoris from Pakistan and it will help to produce more effective vaccine to immunize 180 million people of Pakistan against HBV.